Process for refining sugar.



JOHN G. KREMERS, or mILwAuxnE, wrscousm.

rnoonss non 'nnrrnme SUGAR.

No Drawing.

To all whom it may concern:

Be it known that I, JOHN G. KREMERS, a citizen of the United States, residing at Mil waukee, in the county of Milwaukee and State of lVisconsin, have invented a certain new and useful Improvement in Processes for Refining Sugar,-of which the following is a full, clear, concise, and exact description.

This invention relates to processes of clarifying and refining impure sugar solutions, more particularly sugar solutions in which more or less glucose and combined potash are both present. The refining of such solutions has heretofore been attended with considerable difliculty owing'to the fact that by the methods heretofore practised the potash, at one stage or another of the refining process, has been present in the form of an alkaline reacting compound and has therefore reacted destructively on whatever glucose might be present to give dark colored products whose elimination from the juice and resultant crystallized sugar has been extremely difficult and practically impossible in many instances. It is for this reason, among others, that great difficulty has been experienced heretofore in attempting to produce refined sugar direct from raw cane juices.

One of the main objects of the present invention is to obviate the difliculties heretofore experienced in this respect and to render feasible direct production of refined sugar from raw cane juices comin directly from the mill. The broadprincip es of the invention are also applicable to solutions of sugar derived from other sources, such as partiallyrefined cane suga fillmass, cane syrups, cane ilolasses, etc.

According to ordinary methods of refin-, ing sugar juices, a raw sugar solution is first defecated by treating it with lime and by heating. After removal of the scum, the excess of lime is then removed by passing in carbon dioxid gas, this carbonatation usually taking place in several stages. After separation of precipitated matter, the juice is then concentrated to obtain crystallized sugar. 'Operating in this way, whatever potash there was originally present in the sugar solution is present after the carbonatation either as potassium carbonate or bicarbonate, or it is combined with one or more organic acids present in raw sugar solutions. These organic acids are for the most part very feeble acids, and consequently their Specification of Letters Patent. Applicatioii filed i'uly 30, 1913. Serial No. 781,9 40.

masse-cuite or potassium salts are alkaline in reaction. As a consequence, the potash present as carbonate or as an organic salt reacts with any Patented Aug. 11, 1914 in the sugar solution after defecation is re- Baum contained in a suitable receptacle treated with lime either in the form of milk of lime or as powdered lime in the approximate proportion of three parts of lime (CaO) to one hundred parts of crystallizedsugar by weight. The amount of lime addednaturally depends upon the condition of the particular sugar solution in question, but suflis cient mustbe" added to insure proper filtration and decoloration. The limmg operation is best carried on ata temperature not exceeding about 45 C. -After defecation, the limed solution is then-treated with carbon dioxid gas which is passed into the solution until atest sample shows approximate neutrality to phenolp thaljein or. to an equivalent. indicator of the henolphthalein type. At this point the lime as been substantially all preclpitated as calcium carbonate, while the potash is probably present in combination with the weakorganic acids of the sugar juices. A small amount of lime may also still remain in solution in more or less complex combination. These weakorganic acid potash salts, while not alkaline towardphenolphthalein, are alkaline to litmus; and the reaction of the carbonated solution at this point, although substantially neutral to phenolphthalein, 1s therefore still alkaline to litmus. At this point, the solution is best .transferred to'another treating tank where purposes removed from the field of sulfur dioxid is run in until the solution is substantially neutral to litmus or to an equivalent indicator of the litmus type. In

fact, in some cases, particularly in treating raw cane juices coming directly from the mill, it is distinctly advantageous to go more or less beyond the point of .neutrality to litmus and to render the solution slightly acid in reaction. In this treatment with sulfur dioxid, the organic acid salts of potash are decomposed with the formation of potassium sulfite and the corresponding free organic acids. The presence of these free organic acids in the solution seems to protect the sugar from the harmful effects which might otherwise be experienced from any excess of sulfur. dioxid in the solution. Any lime still remaining after carbonatation is precipitated as calcium sulfite by this treatment.

Instead of using sulfur dioxid or sulfurous acid as above described, phosporic acid may be employed for rendering the solution neu-tral' or somewhat acid to litmus aftercarbonatation has been carried to the point of neutralit' to phenolphthalein. In this case the potas is finally obtained in the form of potassium phosphate. Any residual lime is, of course, precipitated as phosphate when phosphoric acid is used. Both potassium surfite and potassium phosphate are stable salts of neutral reaction and without decomposing effect on glucose at the temperatures employed in concentrating purified sugar solutions.

The steps above described are best carried out at comparatively low temperatures and ordinarily it is advantageous not to exceed about C.

After the treatment above described, the sugar solution may be freed from precipitated matter in any suitable way as, for example, by heating to say 90 C. or higher and then filtering through filter presses or other convenient filtering means. The potash being now resent' in a form non-reactive toward g ucose, the temperature of the solution may be raised to any reasonable extent without fear of darkening its color by destruction of glucose. Consequently the temperatures employed during the filtering operation may be as high asis desirable or convenient to insure rapidity in the filtering operation. The filtered solution may be further treated and purified as desired, or it may be immediately concentrated and the sugar crystallized out in'the ordinary manner.

What I claim is:

1. The proces of treating impure sugar solutions which comprises defecating such a solution by means of lime corbonating until the solution is substantially neutral to an indicator of the phenolphthalein type,

and then treating the carbonated solution with an acid capable of forming a stable neutral salt with potash.

2. The process of treating impure sugar solutions which comprises dcfccating such a solution by means of lime, carbonating until the solution is substantially neutral to an indicator of the phenolphthalein type, and then treating the carbonated solution with sulfurous acid.

3. The proces of treating impure sugar solutions which comprises dcfecating such a solution by means of lime, carbonating until the solution is substantially neutral to an indicator of the phenolphthalcin type, and then treating the carbonated solution with sulfurous acid in quantity at least sufficient to render the solution substantially neutral toward an indicator of the litmus type.

4. The process of treating impure sugar solutions which comprises defecating such a solution with lime, carbonating to a point at which the solution is approximately neutral to phenolphthalein, and treating with sulfur dioxid until the solution is substantially non-alkaline to litmus.

5. The process of treating impure sugar solutions which comprises defecating such a solution with lime, carbonating to a point at which the solution is approximately neutral to phenolphthalein, and treating with sulfur dioxid until the solution is somewhat acid to litmus.

6. The process of treating impure sugar solutions which comprises defecating such a solution with lime, carbonating to a point at which the solution is approximately neutral to phenolphthalein, treating with sulfur dioxid until the solution is substantially non-alkaline to litmus, the solution being maintained at a relatively low temperature during these steps, and thereafter heating and filtering the treated solution.

7. In the purification of impure sugar juices the process which comprises carbonating lime-defecated juice to approximate neutrality toward phenolphthalein, and then treating the carbonated solution with anacid capable of forming a stable neutral salt with otash.

8. In the purification of impure sugar then treating the carbinated solution with ating lim'e-defecated juice to approximate neutrality toward phenolphthalein, and then treatin the carbonated solution with sulfurous acid at least until the. solution is substantially neutral to litmus.

9. In the purification of impure sugar juicesthe process which comprises carbonating lime-defecated juice to approximate neutrality toward phenolphthalein, and then treating the carbonated solution with sulfurous ac1d at least until the solution is substantially neutral to litmus, the solution being maintained at a temperature not higher than about 45 steps.

10. In the purification of impure sugar C. during these juices the process which comprise carbonating lime-defecated juice to approximate neutrality toward phnolphthalein, and then treating the carbonated solution with sulfurous acid at least until the solution is substantially neutral to litmus, the solution 10 being maintained at a temperature not higher than about 415C. during these steps,

thereafter heating, filtering and concentrating the treated solution.

I JOHN G. KREMERS. Witnesses:

J. A. SoHUL'rE, W. H. HEIDEMAN. 

